Bitcoin uses a simple stack-based language called script to describe how bitcoins can be spent and transferred.
It is not Turing complete and has no loops to avoid any undesirable effects of long-running/hung scripts on the Bitcoin network.
The Programmable Logic Behind Every Transaction
This scripting language is based on a Forth programming language like syntax and uses a reverse polish notation in which every operand is followed by its operators.
It is evaluated from the left to the right using a Last In, First Out (LIFO) stack.
Scripts use various opcodes or instructions to define their operation.
Earlier versions of the Bitcoin node had a few opcodes that are no longer used due to bugs discovered in their design.
The various categories of the scripting opcodes are constants, flow control, stack, bitwise logic, splice, arithmetic, cryptography, and lock time.
A transaction script is evaluated by combining ScriptSig and ScriptPubKey.
Why This Matters for Blockchain Technology
ScriptSig is the unlocking script, whereas ScriptPubKey is the locking script.
ScriptSig is provided by the user who wishes to unlock the transaction 3.
ScriptPubkey is part of the transaction output and specifies the conditions that need to be fulfilled in order to spend the output 4.
In other words, outputs are locked by ScriptPubKey that contains the conditions, when met will unlock the output, and coins can then be redeemed
Key Points to Remember
- The script language Bitcoin uses a simple stack-based language called script to describe how bitcoins can be spent and transferred.
- It is not Turing complete and has no loops to avoid any undesirable effects of long-running/hung scripts on the Bitcoin network.
- This scripting language is based on a Forth programming language like syntax and uses a reverse polish notation in which every operand is followed by its operators.
- It is evaluated from the left to the right using a Last In, First Out (LIFO) stack.
Conclusion
The script language represents one of the many innovative layers that make blockchain technology so powerful and transformative. As distributed systems continue to evolve, a solid understanding of these core concepts becomes increasingly valuable — not just for developers, but for anyone building, investing in, or working alongside blockchain-powered systems.
Whether you are just starting your blockchain journey or deepening existing expertise, mastering these fundamentals gives you the tools to think clearly about decentralized systems and make smarter decisions in this rapidly evolving space.